This is her attitude about all authority, no matter how minimal, like the authority a volunteer traffic helper has.
He was "condescending" because he was telling her to stop and she kept coming. So he waved faster and held his hand out for her to stop a moment. That is exactly his job and absolutely nobody else there had the thought about how condescending he is. But he is telling her to do something, she is ignoring him, so he has to tell her again. In her book, this is condescension. She got the same shit from teachers who had to tell her to behave herself and turn in her homework. She got the same shit from bosses who told her to come to work on time and not sneak out early. She got the same shit from doctors who told her that she has to cut down on the eating and get some exercise. Now, she is getting it from some punk who wants her to slow down and make a right.
I loved that moment, because it was so Clotso. You can't fucking ever tell her what to do.